"We also had strong branded postpaid net additions of one million, supported by continued strong growth of wearables, particularly the Apple Watch," Legere said.

The company touted 1.6 million total net additions and 4 percent revenue growth year-over-year for the period.

In their official earnings release, T-Mobile again mentions Apple Watch as the driving force behind a huge increase in "other net customers," meaning users of non-phone devices. That metric increased by nearly 50,000 from the same time last year.

"Branded postpaid other net customer additions were 331,000 in Q2 2018, up 47,000 from Q2 2017," the firm said. "Year-over-year the increase was due to higher gross customer additions from connected devices, specifically the Apple watch."

Later this fall, Apple is expected to release the Apple Watch Series 4, which is rumored to see the line's first major redesign with slimmer bezels and larger screens. The device will likely ship alongside Apple's watchOS 5 firmware, which is currently in testing by developers.